Patent GB-1021025-A (GB)
Title: Fixed message generator for printing telegraph apparatus
IPC: H04L25/04
Filed: 1962-12-04
Abstract: 1,021,025. Telegraphy. TELETYPE CORPORATION. Dec. 4, 1962 [Dec. 14, 1961], No. 45730/62. Heading H4P. In a teleprinter there is provided a fixed message generator which responds to reception of an " answer back " signal or to depression of the " Here is " key, it being arranged that the generator does not respond if the answer back signal is included in local signals generated by means of the teleprinter keyboard. The fixed message comprises the station identification followed by an answer back signal and in order that an unending series of identification and answer back signals shall not be set up means is provided which block the answer back signal if the generator is responding to an answer back signal from a remote station. Transmission from the tape reader.-The teleprinter described includes a tape reader 31 for sending signals to the transmitting distributer 22 and hence to the line. Tape-read starting or stopping is accomplished either by depressing keys 45 or 44, or by contacts 98, 50 which are controlled by the remote station. The reader 81 is also stopped if the tape becomes tight or broken, or if there is a line break. When the reader is started magnet 54 locks up and armature 65 moves anti-clockwise, thereby permitting lever 71 to move clockwise. This action rotates bar 76 and releases clutch 78 so that the distributer sends over the line the signal sensed from the tape. Cam 96 trips lever 71 at each revolution, this closing contacts 74 so that the tape feed magnet is energized. Transmission from the keyboard.-When the teleprinter is transmitting under control of the keyboard depression of any character key unlatches arm 104 which, through various linkages, causes lever 110 to move clockwise to release the clutch. Contact springs 112 are set in accordance with the key depressed and send signals to the distributer for transmission. Cam 97 resets the mechanism when the character has been transmitted. To prevent these contacts interfering with transmission from the tape reader or from the fixed message generator the contacts 112 are urged away from contact bar 113 by lever 115 when no key is depressed. Operation of the receiver and message generator.-Reception of signals from a remote station causes code bars 135 to be set, and if an answer back signal is received the bars set such that lever 136 can move upwards. In doing so it latches on lever 137 and when, during the normal printing operation, bar 139 is driven downwards lever 137 also moves downwards, rotating arm 140, 141 to move bars 143 and 185 to the left. Arm 145 therefore moves clockwise, permitting lever 147 to move clockwise also and to latch over ratchet 149 on the fixed message generator. Rotation of lever 145 releases the distributer 22 so that the ratchet steps at each distributer revolution. The generator comprises a number of radial pins on drum 151 which act on contact springs 117 to set the springs in accordance with the character to be transmitted via the distributer 22. In order that the first character on drum 151 shall not interfere with signals set up by the tape reader or keyboard the contacts 117 are held away from contact bar 150 when the drum is in its rest position, determined by lever 145 latching in a detent in the drum 151. When the drum has completed one revolution lever 145 will be moved anti-clockwise and the distributer will be stopped. If a remote station sends an answerback signal the answer back signal in the drum 151 must be suppressed lest an unending to-andfro exchange of identities is set up. This is done by lever 185 which, on moving to the left as mentioned above, allows contact spring 188 to engage the pins in drum 151, and these pins are so arranged that contact 188 shunts the transmission line where the drum carries the answer back signals. Depression of the " Here is " key 17 also causes the drum to make one revolution, but in this case the answer back signals are not suppressed. When an answer-back signal is set up by the local keyboard the fixed message generator does not operate as it is arranged that lever 136 is now blocked against upward movement. This is done by way of cam 130, which rotates with the distributer, and associated linkwork. When transmitting from the tape reader, the reader must be stopped immediately upon reading an answer-back signal to prevent the reader from interfering with the first station identification character transmitted from drum 151. This is prevented by shunting the transmission line by contact 195.